You've been there before, I'm sure. There you are, playing at your local game store, and you sit down to a game (tournament or otherwise). You play an Island, play Peek, look at your opponent's hand...and proceed to recite his decklist to him, being right 99% of the time. You've just encountered a net-deck, a widely-used construct that has a very good winning percentage. Sure, you're rolling your eyes as you face another tired re-hash of a deck you see twelve times a day, but the problem is that the net-decker is getting precisely what he wants out of it: he wins. And as long as he keeps winning, he's going to keep playing that net-deck and boring you to death.
So, what do you do about it? You could just groan and try to shame the person for his lack of creativity...but the odds are very good that he already knows that his deck is a copy, and simply doesn't care as long as he keeps winning. You could go around to your local play area and suggest that nobody play net-decks, as long as you can withstand a great deal of laughter at your expense (and a total lack of results.)
Now, I'm going to make a revelation that may have many casual Magic players coming for my head, but I'm going to assert it nonetheless: Believe it or not, a field stuffed with predictable decks is your best friend! There's nothing like knowing exactly what's coming your way to give you more than enough time to prepare for it. After all, what war was ever won by the side that told its enemy how many troops it had, what weapons it had, and how and when it was going to use them? I'm going to do my best to help you...not by giving you a decklist (thereby becoming that which I seek to defeat), but by helping you make your own!
STEP 1: KNOW THY ENEMY
You can hate Tog all you want, but unless you realize what the win cards are, you'll never stop it. You can despise Frog until the cows come home, but until you figure out how it wins and why, you won't be able to do anything about it. The key to defeating your least favorite re-hashes is in understanding how, why, and when they win. Frog In A Blender, for example, comes out with a strong early game and is flexible because it can use its burn to finish you off if you stop its creature rush. Meanwhile, Tog wins in the late game, by turning countermagic and card-drawing into two spells in one (using them to their natural effect as well as using them to fuel their Psychatog).
2. UNDERSTAND YOUR FIELD.
Is it worth building a deck that will hand G/U/R Madness its head, if only one guy in your area is playing it? Even moreso, does your area include a vast assortment of rogue decks, making the very practice of building anti-netdecks a lost cause (and suggesting that you simply need a better deck in the first place)? To take advice from Jeff Goldblum from the original Jurassic Park, you should decide whether or not you should make your monster before you worry about whether or not you can and will.
3. UNDERSTAND YOUR OPPONENT'S WEAKNESS.
Remember this: there is no deck that does not have a weakness. Countermagic can be defeated by speed (which is why Frog In A Blender can semi-frequently kick Tog in the head). Creature decks can be handled by mass-removal (Wrath of God) or nullification (Ensnaring Bridge). Once you understand how the decks you expect to face work, you can plan against them. I, for example, have begun using the much maligned Healing Salve against such speed-based strategies as Frog In A Blender or Quickie Beats (a green construct I've found to be annoyingly effective). Speed decks, when denied their speed, will often allow an intelligent player to get their own strategy set up. Which brings us to another point:
4. YOUR DECK MUST BE GOOD
I actually witnessed this at one point: an angry player, having faced one too many Frog In A Blender decks, created a deck meant to stop it in its tracks. And that it did; with four Circle of Protection: Green, four Circle of Protection: Red, four Pacifism, four Wrath of God, and other such spells, said player faced a Frog In A Blender deck and stopped it cold. I watched the match for about ten minutes, then privately said to him, "Well-played, he's stopped cold. How do you win?" He gave me this blank look...then scooped his cards up. He'd been so intent on making his anti-strategy all-encompassing that he'd forgotten to include a good enough win condition; without any flying creatures that could withstand Fiery Temper's angry touch, all his opponent had to do was wait for two Urza's Rages, kick them, and win. This highlights my point: you won't only be facing net-decks (I hope!), so if your deck is too finely tuned, you'll destroy your target and get run over by the first original deck you see.
And that's what it comes down to. It does no good for me to give you a decklist to beat net-decks, any more than it does to give someone a net-deck list and automatically expect him to understand it; card names are no substitute for understanding and playing skill. With time, both will come to you...this article was simply my attempt to jar your intellects into action.
Identify your opponent. Know his weaknesses. Exploit them, and victory will be yours.